The present invention relates to a material-removing tool. More particularly this invention concerns a tool that can be chucked in a hand-held drive unit such as a hand drill.
Although a power hand drill is primarily intended to bore holes, it is known to chuck in such a hand drill a material-removing tool that is rotated drill-fashion but which has lateral material-removing formations that are used to clean out holes or grind away an edge of a workpiece. This particular application of a power hand drill is most often seen in home use where the single power drive unit is used as the motive force for several different types of operations that normally would be carried out by separate units altogether. Thus it is known to fit in the chuck of the hand drill a rasp, a reamer, a rotary milling tool, a drum-type sander or milling tool and various other devices which must be pressed radially relative to the rotation axis of the tool against the workpiece.
Such use of a normally rotary tool has the considerable disadvantage that it is very difficult for the user holding the hand drill accurately to guide it. Thus, sloppy results are often obtained. For this reason the hand drill is obtained. For this reason the hand drill is often mounted in a bench stand so that it is fixed and the workpiece is displaced past it. Such an arrangement is fully unusable in many applications, as it is often impossible due to workpiece size or immobility to move the workpiece past the tool.
Another disadvantage of this type of arrangement is that considerable radial force is applied to the tool. Such radial force can cause the tool to break, not only damaging an often valuable tool but presenting a considerable danger for the user who is applying pressure against the tool. Furthermore such radial pressure puts a considerable load on the bearings of the drill which are often only designed to withstand axial pressure. Thus using the tool for reaming, filing, or milling often results in its premature wearing-out.
Another disadvantage of this type of operation with a hand drill is that the user must often assume a very uncomfortable position. For this reason he or she ties very rapidly and often does an inadequate job merely because fatigue has called a halt to the operation.
I disclose in my above-cited copending patent application a combination with a hand held drive unit having a chuck defining a chuck axis and adapted to move only in a predetermined non-radial manner relative to this chuck axis of a tool having a handle and means for securing the handle to a projection at the end of the tool so that this handle does not move with the tool as the tool is displaced by a chuck, but is in radial force-transmission with the tool. The tool in accordance with this invention has a central tool axis, a material-removing formation, a shank extending axially to one side of the formation and receivable within the chuck with the tool axis and the chuck axis aligned, and a projection extending axially to the other side of the formation. The handle is a simple knob, preferably made of synthetic-resin material and dimensioned so that it can be firmly held by the user in one hand while his or her other hand holds the drive unit. Thus with the system according to the present invention the tool is held to either side of its material-removing formation. This greatly unloads the drive unit, reduces the twisting stress on the tool enormously, and makes it relatively easy to guide the tool accurately.
The arrangement according to my earlier invention may also be used in a simple rotary-type hand drill constituting the drive unit. In this arrangement the projection at the end of the tool is of cylindrical shape and a correspondingly cylindrical hole is formed in the knob. The projection is rotatable within the knob but is axially fixed relative thereto by a pin projection radially inwardly in the hole in the knob into a circumferential groove in the projection of the tool. Thus, the knob can be held rigidly and non-rotatably while the tool rotates at high speed and the material-removing formations on the tool act on a workpiece. The material-removing formation may be milling teeth, a sanding disc, file teeth, reaming formations, or the like.
In accordance with my earlier invention the handle which is rotatable relative to the tool is provided with a pin constituted as the end of a screw threaded radially into the handle. This pin has a diameter which is slightly less than the axial length of the groove in the tool projection and has an end surface which is spaced slightly inwardly of the base of the groove. Thus, there is practically nothing to interfere with the rotation of the tool in the handle. A journal constituted as a bronze or brass bearing in the handle greatly increases the facility with which the tool rotates relative to the handle.
In accordance with further features of this previous invention the tool is provided with a guide that maintains the workpiece removing formation of the tool in a predetermined position relative to the workpiece. This guide can be a stop provided on the tool which engages axially or radially against the workpiece and, therefore, defines a predetermined position axially or radially between the two. The provision of one such radial stop formed as a ring around the tool and another axial stop constituted as a cap axially secured to the tool allows the arrangement to be used to neatly form a groove at the edge of a workpiece.
It is also within the scope of this earlier invention to constitute a guide device as a plate formed with a through-going hole in which the tool is journalled and connected to a guide so that it follows a predetermined path along the workpiece. The plate may be provided with pins that ride on the guide and determine this position and either the pins can be displaceable to vary the setting, or the hole can be formed eccentrically in a disc which may be rotated to vary the distance between the hole and the pins.
With the system according to my earlier filed application, it has been found, for example, possible to reduce the tooth height of a rotary file from between the conventional height of between 0.8 mm and 1 mm to between 0.3 mm and 0.5 mm. In this arrangement a handle having a weight of between 70 g and 120 g, preferably 85 g, is employed. Such an arrangement makes it extremely easy for example, to machine or mill the edge of a wooden board.